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==Introduction==
 
If you have questions about this article, please see this
{{Community|link=https://twitter.com/ST_Muso/status/1391466144138100736|text=Microphone Feedback discussion}}


== What is feedback and how does it occur? ==
== What is feedback and how does it occur? ==
Feedback occurs when the sound from the loudspeaker (or loudspeakers if a microphone is connected to more than one) is louder at the microphone than the sound of the voice.
Feedback occurs when the sound from the loudspeaker (or loudspeakers if a microphone is connected to more than one) is louder at the microphone than the sound of the voice.


This fundamental fact is shown in the figure below. Note that in the diagram an L1 system is shown but the same fundamental fact is true for ANY loudspeaker.
This fundamental fact is shown in the figure below. Note that in the diagram, an L1 system is shown, but the same fundamental fact is true for ANY loudspeaker.
 
[[Image:Feedback fig 1.jpg|800px|Microphone Feedback]]


If you understand this diagram, it is relatively easy to understand how changes in an amplification system and room can contribute to either increasing or decreasing the likelihood of feedback.  
[[Image:Feedback fig 1.jpg|400px|Microphone Feedback]]


If you understand this diagram, it is relatively easy to understand how changes in an amplification system and the room can contribute to either increasing or decreasing the likelihood of feedback.
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== Techniques For Reducing Feedback ==
== Techniques For Reducing Feedback ==
=== Gain Staging ===
=== Gain Staging ===
Your setup should always begin with good gain staging.
Your setup should always begin with good gain staging and with microphones, that starts with [[#Close Microphone Technique|great microphone technique]]. After that, you can consider [[##Gain_Staging_2|gain staging your equipment]].
 
 
=== Close Microphone Technique ===
{{Close Microphone Technique}}
 
=== Vocal Strength ===
In the feedback diagram at the top, it is clear that other things being equal, vocal strength related directly to how loud a system will play before feedback. Said another way, a low-output singer is more likely to experience feedback for a given desired level in the room than a high-output singer.
 
=== Directional Microphones ===
==== Principles ====
 
Choose a '''directional microphone''' to maximize gain‑before‑feedback. A [[Microphone Directionality#Supercardioid_/_Hypercardioid|Hypercardioid/Supercardioid]] pattern provides the strongest focus on the intended source, followed by [[Microphone Directionality#Cardioid|Cardioid]], with [[Microphone Directionality#Omnidirectional Microphone|Omnidirectional]] offering the widest pickup (the least desirable in most live sound applications).


Take two minutes to watch this video by clicking on the picture below.
Directional microphones excel because they emphasize the desired sound—such as a voice or instrument—while naturally reducing sound arriving from other directions. This focused pickup helps maintain clarity and increases the system’s resistance to feedback.


{{Get Plugged In Microphone}}
Most directional microphones also offer a helpful characteristic known as the [[Proximity Effect|proximity effect]]. As the source moves closer to the microphone, low and low‑mid frequencies become fuller and more pronounced. Microphones designed for close‑up vocal use take advantage of this: they deliver a natural tone at close range while reducing low‑to‑mid frequency content from distant sources, including nearby loudspeakers. This selective emphasis further improves feedback performance.
* If you are using an {{Classic}} or {{Model I}} follow the instructions exactly as shown in the video.


* If you are using the {{T1}}, the principles are the same as shown on the video: simply substitute the [[T1_ToneMatch%C2%AE_Audio_Engine#Set_Input_Trim|trim]] on the {{T1r}} for the trim on the Classic or Model I. {{T1 icon}}
Omnidirectional microphones, by contrast, maintain a consistent tone regardless of distance. This can be ideal in studio environments where uniformity is the goal. On stage, however, their equal sensitivity in all directions means they capture more ambient sound and offer less natural rejection of low‑to‑mid frequency energy. As a result, they provide less gain‑before‑feedback than directional designs.


Your first adjustment for any input to your {{T1}} is the Trim setting. The exact position of the Trim will vary depending on signal strength of your input source. The correct setting for any particular source may be different from your other sources.
====Omnidirectional and Unidirectional Microphones====
{{:Microphone Polar Pattern}}


[[Image:T1TrimPots.png|T1® Trim Pots]]
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==== Set Up Your Source ====
=== Effects ===
Set your source at the maximum that it will be when performing.
If you are using vocal effects like reverb, chorus, or delay, turn them off until you can get sufficient [[Gain Before Feedback|gain before feedback]] to get performance level volume. Then add the effects back into the signal chain (one at a time) so you can be aware of the individual impacts that each effect is having on feedback.
* Microphone
==== TC Helicon Vocal Processors ====
:Sing directly into the microphone using close microphone technique (lips just brushing the windscreen). Sing as loudly as you will sing during your performance. You want to set the Trim to work at your maximum volume.
If you are using a TC-Helicon vocal processor and you have the '''Tone''' processing on, you should not use a T1® Microphone Preset. Using both at the same time can reduce your gain before feedback. For more detail see [[:Category:TC-Helicon|TC-Helicon]].
* Instrument
:Turn your input as high as it is likely to go during performance.


==== Set Input Trim ====
=== Monitor Placement ===
Turn the Trim setting up until the Trim Light is solid green with occasional flickers of yellow. Use the Trim lights as your guide. (The exact position of the Trim knob is not important).
{{Monitor Placement}}


[[Image:TrimlightsOK.gif]]
=== Open Microphones ===
Use as few open microphones as possible.  


If you see flickers of red (below), turn the Trim down. You are definitely nearing or in compression. Turn the Trim down until there are no red flickers.  
:Note that each time the number of open mics in a sound system is doubled (1 to 2, 2 to 4, 4 to 8, etc.), the overall gain [before feedback] of the sound system drops by 3 dB. This means that more open mics equals less gain in the PA system.<ref>[https://www.shure.com/en-US/performance-production/louder/feedback-fact-and-fiction Shure - Feedback Facts and Fiction]</ref>


[[Image:TrimlightsNo.gif]]
When a microphone is not in use, if possible, turn it off. If you have a ToneMatch mixer consider using the [[T1_ToneMatch®_Audio_Engine_/_Tips_%26_Tricks#Feedback:_Comp_Gate_.2F_Noise_Gate|noise gate]] to do this automatically.


Bill-at-Bose <ref>[http://bose.infopop.cc/eve/forums/a/tpc/f/7521050644/m/9821050644?r=7191052284#7191052284 Bill-at-Bose Talks about Gain Staging in the Bose® Musicians Community Message Boards]</ref> talks about setting the gain on a {{T1}}.  
=== EQ and Tone Controls ===
Use the high-frequency tone control for the microphone channel carefully. Feedback could occur when this is set too high.


:One difference in gain staging the T1 and the Classic is that the T1 has a three-stage trim LED. It lights up green when signal is present, yellow when you are getting pretty loud (8 to 10 dB of headroom left), and red when you dangerously close to or at full scale.  
=== Instrument Pickups ===
Wherever possible, acoustic instruments should use pickups instead of microphones.  Pickup systems provide much higher [[Gain Before Feedback|gain before feedback]] than microphones.


:In a way, the yellow trim on the T1 is similar to how you treat the red on the Classic. Some yellow during peaks is good on the T1, just like some red on the Classic is good.  
Using pickup can overcome the struggle to keep a consistent and close distance between the microphone and an instrument. Also, an instrument can be a source of feedback as it resonates with the amplified sound.


:If the T1 trim is going red, you should back off, you are definitely nearing or in compression.
=== Distance Between Microphones ===
Another (low priority) design guide-line could be to keep open microphones as far apart as possible. Neighboring systems with open microphones can mutually decrease [[Gain Before Feedback|gain before feedback]].


:A really helpful feature on the T1 is to go to the Prefs/Output Level menu, and see where you are relative to maximum output.
== Techniques specific to the {{L1 family}} ==


==== T1® Trim Pots ====
=== The Benefit of ToneMatch Presets ===
A microphone that is not tonally balanced requires expertise and sophisticated equipment to equalize optimally. ToneMatch takes the guesswork out of getting studio-quality sound from a microphone connected to an L1 system. Equalization attempted by those not necessarily skilled in the art, or with tone controls that are not sophisticated enough, can leave peaks in the tonal response of the microphone -- peaks that are more likely to invite feedback.


{{:T1 ToneMatch® Audio Engine / Trim Pots}}
For this reason, whenever possible, use a microphone with a ToneMatch preset.


=== Close Microphone Technique ===
=== Gain Staging ===
'''Get close to the microphone''' when you want to be loud. No other technique has a big an impact on feedback. Each halving of distance is approximately another 6 dB of [[Gain Before Feedback|gain before feedback]]. This relationship in physics is known as the [[Inverse Square Law]]. This means that the difference between working a microphone at 2 inches, and 1/4 inch is 18 dB, which is more than twice as loud. While good mic technique often involves "working" the microphone at different distances, singers must be mindful of the fact that small changes in distance from the mouth result in very dramatic changes in sound level.
==== L1 Pro and S1 Pro/Pro+ ====
When you sing or play at the loudest you will perform, the channel light should be solid green. Occasional flickers of red are okay. But if you see solid red, turn down the volume. Important: Use [[#Close Microphone Technique|close-microphone technique]]. The farther you are from the microphone, the greater the likelihood of feedback.


In the feedback diagram at the top, getting close to the microphone means getting more <font color="blue">sound from voice</font> which translates to more gain without feedback.
==== T4S/T8S Gain Staging ====
{{T4S/T8S Gain Staging}}


==== {{T1}} ====
{{:T1 ToneMatch® Audio Engine / Gain Staging a Microphone}}


[[Image:Ferrin_eat_mic.jpg|Charlie Ferrin at Bose: Nov. 9, 2007]]


* If you are using the {{T1}}, the principles are the same as shown on the video: simply substitute the [[T1_ToneMatch%C2%AE_Audio_Engine#Set_Input_Trim|trim]] on the {{T1r}} for the trim on the Classic or Model I. {{T1 icon}}


=== Vocal Strength ===
Your first adjustment for any input to your {{T1}} is the Trim setting. The exact position of the Trim will vary depending on signal strength of your input source. The correct setting for any particular source may be different from your other sources.  
In the feedback diagram at the top, it is clear that other things being equal, vocal strength related directly to how loud a system will play before feedback. Said another way, a low-output singer is more likely to experience feedback for a given desired level in the room than a high-output singer.


=== Directional Microphones ===
[[Image:T1TrimPots.png|T1® Trim Pots]]  
Use a directional microphone. [[Microphone Directionality#Supercardioid_/_Hypercardioid|Hypercardioid]] is better than [[Microphone Directionality#Cardioid|cardioid]], which is better than [[Microphone Directionality#Omnidirectional Microphone|omnidirectional]]. All sound waves impinging on the microphone from a direction other than the intended signal is "noise" and will lower the threshold of feedback.


Directional microphones "collect" less sound from directions other than what they're supposed to amplify (the voice, or an instrument) and hence are less likely to feed back.
Take two minutes to watch this video by clicking on the picture below.


In addition, most directional microphones have a strong behavior called [[Proximity Effect|proximity effect]]. This is the strong buildup of bass and low-mid response as the source (say the voice) to microphone distance decreases. For microphones intended to sound natural when the voice is very close -- say one of a number of popular stage vocal microphones -- what this means is that low-to-middle frequencies from sources at a distance, including loudspeakers being used to amplify the voice, are largely rejected by the microphone. This is a real plus in terms of avoiding microphone feedback.
{{Get Plugged In Microphone}}
* If you are using an {{Classic}} or {{Model I}} follow the instructions exactly as shown in the video.


Conversely, an omnidirectional microphone (equal sensitivity to sound coming from any direction) has no proximity effect. This is an advantage often in the studio where the engineer wants consistent tone regardless of distance. But it's a disadvantage on stage in terms of feebdack. An omnidirectional mic collects more sound that's not the target, and because it has no proximity effect is more susceptible to feedback at low-to-mid frequencies than a directional mic.
===== Set Up Your Source =====
Set your source at the maximum that it will be when performing.
* Microphone
:Sing directly into the microphone using close microphone technique (lips just brushing the windscreen). Sing as loudly as you will sing during your performance. You want to set the Trim to work at your maximum volume.
* Instrument
:Turn your input as high as it is likely to go during performance.


=== Effects ===
===== Set Trim Controls =====
If you are using vocal effects like reverb, chorus or delay, turn them off until you can get sufficient [[Gain Before Feedback|gain before feedback]] to get performance level volume. Then add the effects back into the signal chain (one at a time) so you can be aware of the individual impacts that each effect is having on feedback.
Turn the Trim setting up until the Trim Light is solid green with occasional flickers of yellow. Use the Trim lights as your guide. (The exact position of the Trim knob is not important).


If you are using a TC-Helicon vocal processor and you have the '''Tone''' processing on, you should not use a T1® Microphone Preset. Using both at the same time can reduce your gain before feedback. For more detail see [[:Category:TC-Helicon|TC-Helicon]].
[[Image:TrimlightsOK.gif]]


=== Open Microphones ===
If you see flickers of red (below), turn the Trim down. You are definitely nearing or in compression. Turn the Trim down until there are no red flickers.  
Use as few open microphones as possible. When a microphone is not in use, if possible, turn it off. If you have a {{t1}} consider using the [[T1_ToneMatch®_Audio_Engine_/_Tips_%26_Tricks#Feedback:_Comp_Gate_.2F_Noise_Gate|noise gate]] to do this automatically.


=== EQ and Tone Controls ===
[[Image:TrimlightsNo.gif]]
Use the high-frequency tone control for the microphone channel carefully. Feedback could occur when this is set too high.


=== Instrument Pickups ===
Bill-at-Bose <ref>[http://bose.infopop.cc/eve/forums/a/tpc/f/7521050644/m/9821050644?r=7191052284#7191052284 Bill-at-Bose Talks about Gain Staging in the Bose® Musicians Community Message Boards]</ref> talks about setting the gain on a {{T1}}.  
Wherever possible, acoustic instruments should use pickups instead of microphones.  Pickup systems provide much higher [[Gain Before Feedback|gain before feedback]] than microphones.


Using pickup can overcome the struggle to keep a consistent and close distance between the microphone and an instrument. Also, an instrument can be a source of feedback as it resonates with the amplified sound.
:One difference in gain staging the T1 and the Classic is that the T1 has a three-stage trim LED. It lights up green when signal is present, yellow when you are getting pretty loud (8 to 10 dB of headroom left), and red when you dangerously close to or at full scale.  


=== Distance Between Microphones ===
:In a way, the yellow trim on the T1 is similar to how you treat the red on the Classic. Some yellow during peaks is good on the T1, just like some red on the Classic is good.  
Another (low priority) design guide-line could be to keep open microphones as far apart as possible. Neighboring systems with open microphones can mutually decrease [[Gain Before Feedback|gain before feedback]].


:If the T1 trim is going red, you should back off, you are definitely nearing or in compression.


== Techniques specific to the {{L1 family}} ==
:A really helpful feature on the T1 is to go to the Prefs/Output Level menu, and see where you are relative to maximum output.


=== The Benefit of ToneMatch Presets ===
==== ToneMatch Mixer Trim Controls ====
A microphone that is not tonally balanced requires expertise and sophisticated equipment to equalize optimally. ToneMatch takes the guesswork out of getting studio-quality sound from a microphone connected to an L1 system. Equalization attempted by those not necessarily skilled in the art, or with tone controls that are not sophisticated enough, can leave peaks in the tonal response of the microphone -- peaks that are more likely to invite feedback.


For this reason, whenever possible, use a microphone with a ToneMatch preset.
{{:T1 ToneMatch® Audio Engine / Trim Pots}}


=== Tilt the Mic Up ===
=== Tilt the Mic Up ===
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[[Image:MicGoodBad.gif]]
[[Image:MicGoodBad.gif]]


=== Use the T1® Comp Gate to mute the microphone ===
=== Noise Gate  ===
 
Use the Comp Gate ({{T1}}, {{T4S}}/{{T8S}}) to mute the microphone
{{Noise Gate}}
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=== Notch Out a Problem Frequency ===
Use the ParaEQ ({{T1}}, {{T4S}}/{{T8S}}) to Notch out a problem frequency


=== Use the T1® ParaEQ to "Notch out" a problem frequency ===
Sometimes the geometry and configuration of the mic(s) will cause one particular frequency to be reinforced more than all the others, relatively independent of the positioning of the microphone.  By identifying that particular frequency, one can use the T1® to reduce ("notch out") just that one particular "problem" frequency.
Sometimes the geometry and configuration of the mic(s) will cause one particular frequency to be reinforced more than all the others, relatively independent of the positioning of the microphone.  By identifying that particular frequency, one can use the T1® to reduce ("notch out") just that one particular "problem" frequency.
{{:Feedback / T1 ToneMatch® Audio Engine}}
{{:Feedback / T1 ToneMatch® Audio Engine}}


== Does Microphone Sensitivity Affect Feedback? ==
== Does Microphone Sensitivity Affect Feedback? ==
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== Picking a Microphone ==
== Picking a Microphone ==
For the best feedback performance, choose a directional microphone that has a [[ToneMatch]] preset.
For the best feedback performance, choose  
* A [[{{PAGENAME}}##Supercardioid_.2F_Hypercardioid|supercardioid or hypercardioid microphone]]
* A microphone that has a [[ToneMatch]] preset  
* For any L1 model or any ToneMatch mixer, you can use a condenser or dynamic microphone.
* For an [[S1 Pro+]] / [[S1 Pro]] use a [[Dynamic Microphones|Dynamic Microphone]]. The S1 Pro family to not support condenser microphones
* For more insights, please see [[Review / Microphone / Various|Microphone Reviews]].


== Feedback Destroyers ==
== Feedback Destroyers ==
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== Other References ==
== Other References ==
Here's a quick link to other articles about <categorytree mode="pages" hideroot="off" namespaces="Main">Feedback</categorytree>
<!--
* [http://www.shure.com/stellent/groups/public/@gms_gmi_web_ug/documents/web_resource/us_pro_mics_for_music_sound_ea.pdf Microphone Techniques for Live Sound Reinforcement] Shure Educational Publication 2006 39 pages - pdf format
* [http://www.shure.com/stellent/groups/public/@gms_gmi_web_ug/documents/web_resource/us_pro_mics_for_music_sound_ea.pdf Microphone Techniques for Live Sound Reinforcement] Shure Educational Publication 2006 39 pages - pdf format
- [http://bose.infopop.cc/eve/forums/a/ga/ul/5711082304/us_pro_mics_for_music_sound_ea.pdf  alternate source for above]
-->
*[[Media:us_pro_mics_for_music_sound_ea.pdf|Microphone Techniques for Live Sound Reinforcement]] pdf format
*[https://www.shure.com/en-US/performance-production/louder/feedback-fact-and-fiction Shure - Feedback Facts and Fiction]
* [https://www.shure.com/en-US/performance-production/louder/how-to-control-feedback-in-a-sound-system How to Control Feedback (Shure)]
<!-- [http://bose.infopop.cc/eve/forums/a/ga/ul/5711082304/us_pro_mics_for_music_sound_ea.pdf  alternate source for above] -->
* [http://www.shure.com/ProAudio/Resources/HowToUse/us_how_to_use_vocalmiking Vocal Miking Problems and How To Solve Them]
* [http://www.shure.com/ProAudio/Resources/HowToUse/us_how_to_use_vocalmiking Vocal Miking Problems and How To Solve Them]
* [http://www.shurenotes.com/issue27/article.html Debunking Common Audio Myths] (related to microphones)
* [http://www.shurenotes.com/issue27/article.html Debunking Common Audio Myths] (related to microphones)
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